Preface
The Mass, its sources, edition, completion, reconstruction
Mozart’s Mass in C minor K. 427 (1783) is his last, longest, and most
richly scored setting of the mass ordinary.1 It is also an incomplete work.
In the autograph score (source M), the first half is complete but in the
second half some movements are incomplete while others are missing
altogether. The subdivided Credo only contains a “Credo in unum Deum”
and an “Et incarnatus est”, both composed in outline but with unfinished
instrumentation. All that survives of the Sanctus and Benedictus is Mozart’s separate wind and timpani score for the Sanctus, with segni indicating the partial repeat of the “Osanna” after the Benedictus. This shows
that these movements must have been finished. Their main score, containing the eight vocal and four string parts of the Sanctus and all of the
Benedictus, however, has gone lost.2 There is no Agnus Dei.
Fortunately, two secondary sources survive as well: an organ part and
three trombone parts written by the Salzburg copyists Joseph Estlinger
and Felix Hofstätter (sources E and H), who worked for the Mozarts regularly, and a score copy made around 1800 by the Augsburg choirmaster
Matthäus Fischer (source F). These sources, however, still do not make
all the existing movements complete. In F, for instance, the “Osanna”
double fugue for double choir lacks four of its eight voices and the viola
part. On the other hand, F does contain the complete Benedictus. Details
about the sources can be found in the Critical Report (pp. 173ff.).
To create a performing version of the C minor Mass, at least two tasks
need to be fulfilled: completion of the instrumentation of the “Credo in
unum Deum” and “Et incarnatus est” and a reconstruction of the Sanctus.
Some available editions also offer additional movements to complete the
mass cycle. This edition concentrates on the movements for which substantial source material is available.
The two Credo movements are not included in the secondary sources,
E, H, and F. Clearly, they were not finished at the time of the only known
performance of the Mass during Mozart’s life, on 26 October 1783 in
Salz­burg, and were passed over (or replaced by other music). But they
are complete as compositions, with only their instrumentation having to
be finished. For this task, models can be found in similar works by Mozart
himself or composers who may have inspired him.
Characteristically for Mozart, the “Credo in unum Deum” combines
Handel’s elated spirit and resourcefulness with Bach’s serious tone, wellplanned modulating harmonic trajectory and technical thoroughness.
The string and wind parts are incomplete and there are no parts for the
trumpets and timpani that are so distinctive to a Credo in a missa solemnis. In completing these parts, this edition has drawn on similar numbers
by Bach, such as the “Cum Sancto” from the B-minor Mass and the opening choruses of the Magnificat, the Christmas Oratorio, and Cantatas
such as BWV 34, 69, 91 and 137.
The completion of the soprano aria “Et incarnatus est” was inspired by
similar compositions by Mozart himself, such as the arias “Se il padre
perdei” and “Zeffiretti lusinghieri” from Idomeneo (1781), as well as the
slow movements of some piano concertos and symphonies from around
the same time, such as the concertos K. 451, 459, 467, and the “Linzer
Symphony” K. 425. Its intimacy is underlined by the use of mutes in the
upper strings. Additional horns (ad libitum) supply warmth as in K. 451,
459 and 467.3

The Sanctus is written for double choir and its “Osanna” is an eight-part
double fugue for which models are hard to find. Its reconstruction appears to require a total rethinking of the distribution of the melodic material as well, not just the adding of four voices. This prompted a thorough
study of the centuries-old tradition of writing for double choir. Four examples of double fugues for double choir served as models: one from a
Te Deum in C by Antonio Caldara and the others from Johann Christian
Bach’s Requiem Introitus and Kyrie in F, and Dies irae in c, all music that
Mozart may very well have known.4 In line with a tradition that goes back
as far as the Renaissance technique of pairwise imitation, both Caldara’s
and J.C. Bach’s settings consistently present their subject pairs together
in one choir, with the entries spread as equally as possible among all the
voices. This edition applies the same principles in the “Osanna” fugue.
Most of the existing editions split each subject pair, assigning each subject to a different choir.5

“Nothing but Handel and Bach”
Influences of Bach and Handel are clearly audible in many movements of
the C-minor Mass. The reason for this is obvious. Mozart had moved to
Vienna in the spring of 1781 and, in his letters of April 1782 to his father
and sister in Salzburg, he enthusiastically reported his participation in
the Sunday noon meetings organized by the diplomat and court librarian
Gottfried van Swieten. Van Swieten was also a music enthusiast and
had collected many copies of Bach and Handel works while serving as
the Austrian ambassador in Berlin from 1770 to 1777. “Nothing is played
there but Handel and Bach”, Mozart wrote, and “Baron Van Swieten [...]
gave me all the works by Handel and Sebastian Bach to take home after
I had played them through for him.”6
Van Swieten’s Bach collection probably contained Das Wohltemperirte
Clavier (at least the fugues), the English and French Suites, the Inventions,
Das Musikalische Opfer, Clavierübung III, the Six Trio Sonatas for organ,
the St. Matthew Passion, the Magnificat, and the B-minor Mass.7 On
20 April Mozart also wrote to his sister that Constanze (whom he was
to marry in August 1782) was absolutely “in love with” fugues and urged
him to compose them himself. This resulted in pieces such as the Prelude and Fugue K. 394 and indeed the “Cum Sancto” and “Osanna” fugues
for the C-minor Mass. The “Crucifixus” from Bach’s B-minor Mass, with its
chromatic lamento bass, must have been a great inspiration for Mozart’s
“Qui tollis”. But the lamento is present in other movements of the C-minor
Mass as well: first as a bass line and later as a fugato subject in the Kyrie,
in the “Gratias”, the “Domine Deus” (the Kyrie’s lamento fugato subject in
diminution) and a diatonic version in the “Quoniam”. Also, near the end of
the “Cum Sancto”, the ascending chromatic bass line can be heard as an
inverted lamento. The spirit of Bach’s “Cum Sancto” seems to reappear
in Mozart’s “Credo in unum Deum”. A striking overall similarity between
Bach’s B-minor- and Mozart’s C-minor Mass is the choral disposition in
four, five, and eight parts.
Mozart must have known some of Handel’s works before he moved to
Vienna, certainly his Messiah, which we know he heard in Mannheim. He
quotes its “Halleluja” almost literally in the “Gloria in excelsis Deo” of the
C-minor Mass. But Van Swieten’s collection contained more of Handel’s
oratorios,8 including probably Israel in Egypt, one of the few that uses

VIII
a double choir. We know that four movements of this work, including
“The people shall hear”, were performed on 22 and 23 December 1782 in
concerts organized by the Tonkünstler-Societät (a pension fund for the
widows and children of Viennese musicians).9 The influence of “The people shall hear”, its relentless dotted rhythm (symbolizing scourging and
penance), can clearly be heard in the “Qui tollis”, together with a chromatic lamento bass like in the “Crucifixus” from Bach’s B-minor Mass. The
main subject of Mozart’s “Osanna” is similar to the subjects of the chorus
“Ein jeder sei ihm untertänig” from Handel’s Brockes-Passion, the Allegro
of the first movement of Handel’s Concerto grosso Op. 3/3 and the final
“Amen” fugue from Messiah.
Van Swieten’s collection also contained works by Bach’s sons. The influence of C.P.E. Bach’s cantata Heilig ist Gott is audible in K. 427’s “Gloria
in excelsis Deo” and “Qui tollis” (the subito pianos!).

Origin and unfinished state
In spite of received opinion, we can actually only guess at Mozart’s original incentive to compose the C-minor Mass. Neither do we know the
reason why he never finished it. The only time Mozart mentions the Mass
is in a letter to his father of 4 January 1783, where he links it to some unspecified promise: “[...] – As to the moral, you are right. It did not flow from
my pen without purpose. In my heart I really promised it and I really hope
to keep my word. When I promised it, my wife was still single. But since I
was absolutely determined to marry her soon after her recovery, I could
easily promise it. Time and circumstances however thwarted our journey,
as you know yourself. But the score of half a mass, lying here in the best
of hopes, can serve as proof of the truthfulness of my promise.”10
Exactly what Mozart promised must have been discussed in preceding
letters. Those from Leopold, however, in which he apparently reminded
Wolfgang of his promise, have not survived. And Wolfgang’s earlier or
later letters do not shed any more light on the question. What we do
know from his letters of 7 and 24 August 1782, however, is that he and
Constanze planned to visit his father and sister in Salzburg shortly after their wedding, well before Constanze’s first pregnancy, which we only
hear of in Mozart’s letter of 13 November. This is interesting because, in
unpublished material for a Mozart biography Constanze sent to Breitkopf
& Härtel around 1800, she wrote: “When his wife was pregnant for the
first time and he wanted to take her to his father in Salzburg, he promised
that when both would go off happily, he would write a mass there.”11
Both Wolfgang’s and Constanze’s statements link the promise to the
visit to Salzburg. But while Mozart dates it to before their wedding and
does not explicitly say the Mass had been part of it, Constanze claims it
was made during her pregnancy and clearly mentions the Mass as being
the promise and her successful confinement as a condition.
Clearly, Constanze’s version of the story has led to the conviction of
many Mozarteans, starting with Nissen and the Novellos, that the Mass
was conceived as a ‘votive mass’ for Constanze. However, given that the
Salzburg visit was originally planned to take place soon after the wedding
and that the Mass was only half-finished by 4 January 1783, this seems
a little doubtful. Mozart may have promised some kind of a composition
for the occasion and decided only in January 1783 that the Mass should
serve this purpose. In the end he and Constanze only arrived in Salzburg
on 29 July 1783, six weeks after the birth of little Raimund, and stayed
there until 27 October. The child was given into care in Vienna, where he
sadly died in August.12 The finished movements of the Mass were performed in St. Peter’s Abbey Church on Sunday 26 October.13
But there are more reasons for doubt. The huge dimensions of the
Mass makes one wonder how Mozart could have conceived this work for
Salzburg. Its scoring for double choir and an unusually large orchestra
suggests he had a big church in mind. The ideal setting for it in Salzburg,
the church Mozart was accustomed to writing for, was of course the cathedral, with its four organ balconies around its spacious crossing. All the
instrumentalists and the conductor were positioned on them, with the
choir on the presbytery floor. But the cathedral was now out of the question: it was the domain of the hated Archbishop Colloredo, whose service
Mozart had left following a heated dispute two years before.14 St. Peter’s
Abbey Church, however, where the Mass was finally performed, is long
and narrow, and musical performances in it were usually given with the
musicians positioned in the single organ gallery above the entrance. This
gallery could hardly have accommodated the Mass’s complete forces.
Besides, a double choir, with its characteristic antiphonal effects, would

have made little sense in such a setting. St. Peter’s, then, seems to have
been a last resort, an emergency solution.
Another issue is the rather tragic character of the Kyrie and much of
the Gloria, with their ample use of the minor mode and lamento basses,
which are exceptional for Mozart. It was not without reason, apparently,
that Mozart later set the Kyrie and Gloria to an Italian version of the penitential Psalms of David, in his cantata Davide penitente, K. 469, for concerts of the Tonkünstler-Societät. That the same music should have been
conceived for celebrating a wedding seems odd. Various scholars have
therefore looked for another possible reason for the initial composition:
a commission, perhaps, from one of Vienna’s brotherhoods, e.g. that of
St. Cecilia, which organized big musical events in St. Stephen’s Cathedral
every 22 November. No evidence, however, has been found so far.
Once Mozart had decided the Mass would serve the Salzburg visit
(which makes it a very personal work), he may have seen it in part as
a late commemoration of the sudden death of his mother during their
stay in Paris in 1778, and as a gesture of compassion towards his father,
who had suffered so many setbacks. It must also be said that the tragic
aspect of the work is strongly complemented by the grandiose and exhilarating major-mode music that frames the Gloria and dominates the
second half of the work. Furthermore, the massive fugues must have
been to Constanze’s taste (if we are to believe Mozart’s word on this). Finally, Mozart may also have composed the Mass out of pure love for the
music and have seen it as his tribute to his beloved great masters of the
past. Constanze was probably quite right when she wrote around 1800:
“He wrote it, and he loved it so much himself that he always showed it con
amore to masters who visited him afterwards.”15
Why, then, did he not finish it? There are several possible reasons. First
of all, under Austria’s enlightened rulers, masses of such length had already been out of favour for a number of decades. In a letter written in
September 1776, Mozart described to Padre Martini how in Salzburg
even solemn masses (with trumpets and timpani) were not supposed to
last more than 45 minutes including all spoken words and an epistle sonata. His most recent Salzburg masses, K. 317 (“Krönungsmesse”) and
K. 337 (“Missa in C”, also called “Missa solemnis”), clearly satisfied this
requirement.
Equally clearly the C-minor Mass does not, which suggests it was written for a special occasion. If this was a celebration of one of the Viennese
brotherhoods, the reason for its remaining unfinished must be the fact
that Emperor Joseph II had abolished all brotherhoods by June 1783.
And Joseph’s Gottesdienstordnung, issued a few months earlier, which
imposed rigorous restraints on Vienna’s extravagant use of instrumental
music in church services, had already shrivelled the prospects of further
performances to almost nothing.
If, on the other hand, the Mass was a private affair – which it indeed became from January 1783 onwards –, Mozart may simply not have been
able to find enough time to work on the Mass while trying to survive as a
freelancer in a highly competitive environment. As to the unfinished Credo, there may have been some confusion whether a Credo was required
on the actual Sunday of the Salzburg performance.16 Another factor may
have been the death of the couple’s first child: they must have been devastated and Mozart may well have found it difficult to continue (after the
“Et incarnatus est”, of all movements!). On the other hand, “there are also
instances of Mozart coping with the greatest of bereavements [...] and
maintaining his usual remarkable productivity”.17

Venues, performance strengths, placement
In Mozart’s times no standard sizes existed for either choirs or orchestras. Numbers of soloists and obbligato instruments were of course determined by the composer, but the strengths of choirs and string sections largely depended on the occasions, genres, and venues themselves.
Much is known about this from reports such as Leopold Mozart’s Nach­
richt von dem gegenwärtigen Zustande der Musik Sr. Hochfürstlichen
Gnaden des Erzbischoffs zu Salzburg im Jahr 1757 and from musicians
payment lists and sets of parts that survive in the various archives in
Salzburg and Vienna.18
In the spacious Salzburg Cathedral, the venue Mozart was most used
to writing for, solemn masses were performed by the ‘Hofmusik’, which
according to Leopold’s report consisted, apart from soloists, of 30 to 45
singers (boys and men) and a string section of roughly 4-4-2-2-2.19 In the
much smaller St. Peter’s Abbey Church, however, the choir was made

IX
up of a mere 12 or so singers and an orchestra of just one or two first
and second violins, no bassoons and only rarely horns, trumpets, timpani
and trombones. In view of this, Nannerl Mozart’s diary note on the 1783
performance of K. 427 (“die ganze hofmusik war dabey”) is even more
telling: they couldn’t have done without.20 Fischer’s score copy (F) shows
that the original set of parts contained all the instruments in Mozart’s
full score, including the trombones. This only deepens one’s curiosity as
to how many musicians Mozart actually managed to crowd into St. Peter’s organ gallery and how the Mass finally must have sounded. In any
case, it hardly seems to make sense to now ‘re-enact’ this one and only
performance given during Mozart’s lifetime in the ‘original’ location. Furthermore, any church of similarly modest size and narrow design simply
cannot do the work full justice.
In Vienna, church orchestras and choirs seem to have been rather
small. Their string sections could vary from one to a part, to about 4-4-(21-)1.21 And most of the church choirs “consisted of one, or at most two
singers on a part”.22 However, it seems likely that larger string groups
could be organized for special occasions. Most theater orchestras had
a string section of 6-6-4-3-3. And since all the members ideally played
along, the concerts in the Kärntnertor- and Burgtheater of the Tonkünstler-Societät (for which Mozart prepared Davide penitente in March 1785)
normally featured huge orchestras, with doubled winds and string sections of around 20-20-7-7-7.23 Choir sizes must have been enlarged accordingly. Since Mozart apparently was quite flexible about performance
strengths, there seems to be no reason why we should not be as well.
Another question is the placement of the choir(s) and the strings. Most
orchestras in Mozart’s times seem to have had their two violin sections
at opposite sides, as described by contemporary theorists like Koch and
Petri, as well as by Haydn.24 In addition, an ideal venue for the C-minor
Mass, church or theater, would also be one with enough space to position the two choirs at some distance from each other, to do justice to the
antiphonal character of the double-choir movements.

General editorial issues
Text
Mozart’s rendering of the text of the ordinarium missae has been amended to conform to the Graduale Romanum. This concerns spelling, syllable division, and punctuation. An exception has been made for the word
“Hosanna”. This edition adheres to the Italian form “Osanna” to be found
in the sources of most masses of Haydn and Mozart, including Fischer’s
score copy of K. 427 and Süssmayr’s completion of Mozart’s Requiem.
Clefs
In the vocal staves, Mozart’s soprano and alto clefs have been replaced
by treble clefs and tenor clefs by ‘false’ treble clefs, indicating transposition an octave down. In the Organo/Bassi staff, all C-clefs in basso seguente passages have been replaced by treble clefs.

Identification of editorial additions and provenance of source material
In the conducting score (PB 5562) and the study score (PB 5596), material taken from the three main sources M, E, and F (H is of little value)25 is
in black typeface while all editorial additions (completed or reconstructed material, added articulation, dynamics, figuration etc.) are in grey. In
the “Credo in unum Deum” and the “Et incarnatus est”, all material other
than Mozart’s is editorial. In the Sanctus and Benedictus additions stemming from the three sources are specified by corresponding source sigla
(M = Mozart, E = Estlinger, and F = Fischer). For practical reasons, the
vocal score (EB 8654) and the instrumental parts (OB 5562) are entirely
in black typeface.
In the study score, the full score and the parts, small print is used for
two purposes only: (a) for grace notes, and (b) for three piano passages
in the trombone parts where it is uncertain whether or not Mozart wanted to include the trombones (see “Trombone issues” below).
Grace notes
Mozart writes 16ths, 32nds etc. with one flag and one or more slashes, for
both normal and grace notes. This is why it is not possible to distinguish
between long and short grace notes. Performance decisions should be
based on the context. In bars 6 and 83 of the “Et incarnatus est”, short
performance is recommended. Mozart does not always write slurs from
grace notes to the main note. This edition adheres to the original notation.

Accidentals
In principle, this edition adopts Mozart’s accidentals. Yet it sometimes
adds cautionary accidentals where they seem useful and in accordance
with Mozart’s normal practice and omits superfluous ones (e.g. where
Mozart repeats them in the same bar).
Articulation
Staccato (detached) articulation is indicated in this edition by strokes only,
thus following the prevailing doctrine of today’s scholars such as Clive
Brown and Robert Riggs who have argued against the possibility of clearly distinguishing between dots and strokes as used in eighteenth-century
music. In his Violinschule, Leopold Mozart only uses strokes for staccato.
He only uses dots as part of the portato indication for repeated notes
(dots beneath a slur).26
Articulation signs and dynamics omitted by Mozart (possibly forgotten or taken for granted) but used in similar passages elsewhere in a
movement are added by analogy (in grey in the conducting score and the
study score), but only where there can be little debate on the question of
whether or not Mozart intended a different articulation.
Trombone issues
An ambiguity occurs in the “Gloria in excelsis Deo” (bb. 23–34/1 and 45–
56/1) and in the “Gratias” (bb. 6/3–8/1), where a piano passage between
forte passages suggests a tacet of the trombones, as happens in many
similar cases in other sacred works by Mozart, including the Kyrie (b. 27)
and the “Qui tollis” (b. 14/3) of this Mass. Yet Mozart did not write “senza tromb:” and “tromb:” here. This edition gives these passages in small
print, thus leaving it to performers whether or not to let the trombones
participate.
Another question is whether the trombones should follow repeated
notes in the voices exactly or elide them into a longer note. Mozart’s notation of the wind doublings of the main subject of the “Osanna” fugue
of the Sanctus (bb. 18ff. in the separate wind score at the back of the
autograph) shows that he prefers the latter. In the vocal part, a repetition
of the highest note of the main subject is necessary in order to fit in the
syllable “-san-“. A few notes later we see a tie because now there is no
need for the repeated note. In the bassoon and trombone parts however,
Mozart ties these notes both times, in order to achieve an exact melodic
sequence. A similar situation occurs in the Kyrie (bb. 9–11 Soprano, 13–
15 Alto, and 18–20 Tenore). The subject has a tied note over the bar line
first, lengthening the syllable “Ky-“, then, in the sequence, a repeated note
for the syllables “e-lei-“. Here, and in similar places, this edition follows
Mozart’s example in the Sanctus and gives the trombone (and eventual
other instrumental doublings) a tied note accordingly.
Issues concerning the upper strings
In spite of Mozart’s incidental use of multiple stems for multiple stops,
the two violin parts never seem to be intended as divisi. Mozart’s multiple
stemming in these parts is inconsistent and seems rather arbitrary. He
also uses multiple stemming in each of the two soloistic parts of the
Duos for violin and viola, K. 423 and K. 424 written in the summer of 1783.
Moreover, all of the multiple-stemmed chords in this Mass are well-playable as non divisi multiple stops. The viola part, on the other hand, incidentally is clearly intended to be played divisi, as shown by passages of
two-part writing in the Kyrie (bb. 21–23, 80–83, and 93f.) and the “Laudamus te” (bb. 32–36 and 103–114; bars 109f. are impossible as double
stops). Passages in the Sanctus such as bars 7–11, which are playable
as double stops, seem also more likely to be intended as divisi, enabling
a more fluid linearity. Therefore this edition, as many others, consistently
uses single stemming for the violin parts, but double stemming (where
pertinent) for the violas.
Organ issues
The indications “Solo” and “Tutti” in the organ part had a special meaning in Salzburg. As Leopold Mozart describes in his Nachricht von dem
gegenwärtigen Zustande der Musik Sr. Hochfürstlichen Gnaden des Erzbischoffs zu Salzburg im Jahr 1757, two organs were used for performing instrumental music in Salzburg Cathedral. One of these was one of
the organs placed on the balconies attached to the columns around the
crossing of the church: the organ on the balcony next to the altar on the
right-hand side. The other was a small organ placed on the floor in the
presbytery, where the choir was positioned. The organ on the balcony

X
was the “organo concertato”; and the one on the floor the “organo ripieno”
for supporting the choir. The performance material of most of Mozart’s
masses for Salzburg Cathedral contains separate parts for each of them.
In the score, the indication “Solo” meant that just the organo concertato should play, while “Tutti” included both organs, normally in the choral
passages.
The use of two organs, however, was not very widespread. In most
other churches only one organ was used, as was the case in St. Peter’s
Abbey Church, where the C-minor Mass was performed. It is not entirely
clear what Mozart had in mind when he wrote the Solo and Tutti markings in the score of the C-minor Mass. Did he write these indications out
of habit, or in the hope that the Mass might one day be performed in a
big church with two organs? We can only guess. With one organ, the indications can still function as hints for registration or thickness of texture.

Acknowledgements
This project started in the Mozart Year 2006, with a series of eight performances of the first version of this completion of the C-minor Mass
given throughout Europe by the Netherlands Chamber Choir and the
Orchestra of the Eighteenth Century under Frans Brüggen. It was an extremely fruitful collaboration followed by many other performances in
the ensuing years: by the Brabants Koor and Orkest under Jos van Veldhoven, the Swedish Radio Choir and Symphony Orchestra under Andrew
Manze, the Swedish Radio Choir and Gävle Symphony Orchestra under
Peter Dijkstra, and the Chor des Bayerischen Rundfunks and Münchener
Kammerorchester under Peter Dijkstra, the latter being coupled with a
recording for Sony, the CD of which was issued in 2013. When Cappella
Amsterdam and the Orchestra of the Eighteenth Century performed my
completion under Daniel Reuss in commemoration of Frans Brüggen in
October 2014, the preparations for this edition were already well under
way. Two further performances followed in 2015 by the Bachchor and
Bachorchester Wiesbaden under Jörg Endebrock and in 2017 by Gli Angeli Genève under Stephan MacLeod, now from pre-prints of this edition.
My deep thanks go to all these conductors, singers, instrumentalists and
their orchestra managers for giving me the opportunity to hear whether
what I had conceived really worked in practice and for providing me with
their many wise and insightful comments.
These performances went hand in hand with my teaching responsibilities at the Conservatory of Amsterdam, where I enjoyed warm support
from many colleagues, and the writing of a doctoral dissertation entitled
Mozart’s Unfinished Mass in C minor, K. 427 (‘Great Mass’): History, Theory,
and Practice of its Completion. During the long process of working on it,
I received invaluable support and excellent advice from my supervisors
Rokus de Groot and Manfred Hermann Schmid. Special thanks also go
to David Black, outstanding specialist on Mozart’s sacred music, for generously sharing his knowledge with me, and to Clemens Kühn, Cliff Eisen,
and John Butt, external experts on the doctoral committee.
Last but not least I want to thank Christian Rudolf Riedel (Breitkopf &
Härtel) for the superb craftsmanship and endless patience with which he
supervised the realisation of this edition and for his German translation
of this Preface.
The edition is dedicated in gratitude to the memory of Frans Brüggen
(1934–2014), ‘the magician’, from whom we all have learned so much.
Amsterdam, Spring 2018

Clemens Kemme

1 The unfinished settings of four Kyries and a Gloria from the period 1787-1791 (?)
are not counted here.
2 Mozart’s normal working routine was to notate a composition’s entire melody and
bass parts first and only then turn to the accompanying instruments. In pieces for
voices and orchestra, he notated the entire vocal setting and the orchestral bass
first.
3 For a detailed discussion of this completion, see Clemens Kemme, The “Et incarnatus est” from Mozart’s Mass in C minor K. 427. What Can Be Learnt from a Fragment,
in: Mozart-Jahrbuch 2013 (2014), pp. 65–92.
4 Caldara’s music was well known both in Salzburg and in Vienna. He had been in
Salzburg in 1712 and, from 1716, worked in Vienna as Vize-Kapellmeister to the
Imperial Court under Hofkapellmeister Johann Joseph Fux. J.C. Bach had been

mentoring the young Wolfgang during the Mozarts’ long stay in London in 1764–
65. J.C. Bach had studied with Padre Martini in Bologna and had worked in Milan,
where he wrote most of his sacred works. Mozart may very well have known
these works. And we know he followed J.C. Bach’s example in taking counterpoint lessons from Padre Martini in 1770.
5 As to the subject distribution, only the edition of Richard Maunder (Oxford, 1990)
adheres to the tradition I describe – at least in principle (unfortunately, one
voice lacks an entry of the main subject). Maunder’s versions of the two Credo
movements, however, have met with serious criticism. For an overview of subject distributions in the various existing editions, see: Clemens Kemme, Mozart’s
Unfinished Mass in C minor, K. 427 (‘Great Mass’). History, Theory, and Practice
of its Completion, PhD diss., University of Amsterdam, 2017, http://hdl.handle.
net/11245.1/16b91561-514e-4d42-9e03-0166f6701c3b, pp. 190f.
6 Mozart’s letters to his father of 10 April 1782 and to his sister of 20 April 1782.
Wilhelm A. Bauer / Otto Erich Deutsch (eds.), Mozart: Briefe und Aufzeichnungen,
vol. III, Kassel etc., 1963, pp. 201f. [= MBA III/201f.]. All English translations of
Mozart’s letters by this author.
7 See Andreas Holschneider, Die musikalische Bibliothek Gottfried van Swietens, in:
Georg Reichert and Martin Just (eds.), Bericht über den internationalen musikwissenschaftlichen Kongress Kassel 1962, Kassel, 1963, pp. 174–178; Christine
Blanken, Die Bach-Quellen in Wien und Alt-Österreich. Katalog, Hildesheim, 2011;
Ulrich Leisinger, Haydn’s Copy of the B minor Mass and Mozart’s Mass in C minor:
Viennese traditions of the B minor Mass, in: Yo Tomita, Robin A. Leaver and Jan
Smaczny (eds.), Exploring Bach’s B minor Mass, Cambridge, 2013, pp. 217–243.
8 Van Swieten had organized a performance of Judas Maccabaeus in 1779. In 1788–
1790, he commissioned Mozart to arrange four other Handel oratorios: Acis and
Galatea, Messiah, Alexander’s Feast, and Ode for St. Cecilia’s Day.
9 David Black, Mozart’s Association with the Tonkünstler-Societät, in: Simon P. Keefe
(ed.), Mozart Studies 2, Cambridge, 2015, pp. 55–75.
10 MBA III/247f.
11 Quoted here from: Ulrich Konrad, Die Missa in c KV 427 (417a) von Wolfgang
Amadé Mozart: Überlegungen zum Entstehungsanlass, in: Kirchenmusikalisches
Jahrbuch 92 (2008/2009), p. 112 (English translation by this author).
12 When and how the Mozarts heard about this is unknown.
13 The performance of “the mass of my brother” was reported in Nannerl Mozart’s
diaries: MBA III/290. A letter by Constanze of 31 May 1800 to the music publisher
Johann Anton André (MBA IV/356) confirms it was the C-minor Mass: “Regarding
the Mass related to Davide penitente you should enquire in Salzburg where it
was composed or performed.” Mozart indeed re-used the Kyrie and Gloria for his
cantata Davide penitente of March 1785.
14 Mozart was even afraid of being arrested in Salzburg, as he had never been given
his official discharge, and therefore proposed to meet somewhere else (letters
dating from May 1783). Leopold apparently talked him out of this fear.
15 Quoted from: Konrad, Entstehungsanlass (see fn. 11), p. 112.
16 26 October was the feast of St. Amandus, Bishop of Worms, and on some saints’
days the Credo was omitted. In 1783, however, 26 October fell on a Sunday,
which may have required a Credo anyway. See David Black, Mozart and the Practice of Sacred Music, 1781–91, PhD diss., Harvard University, 2007, pp. 108f., also
available online at https://www.academia.edu/11604023/Mozart_and_the_Practice_of_Sacred_Music_1781-91.
17 Black, Practice of Sacred Music (see fn. 16), p. 125.
18 For detailed information, see: Manfred Hermann Schmid, Mozart und die Salzburger Tradition, Tutzing, 1976, pp. 251–254; Neil Zaslaw, Mozart’s Symphonies.
Context, Performance Practice, Reception, Oxford, 1989, pp. 550–557 (Appendix
C, i.e. Zaslaw’s English translation of Leopold Mozart’s Nachricht, originally appearing in: F.W. Marpurg, Historisch-kritische Beyträge zur Aufnahme der Musik,
Berlin, 1757); Cliff Eisen, Mozart’s Salzburg Orchestras, in: Early Music 20/1
(1992), pp. 89-95; Dexter Edge, Mozart’s Viennese Orchestras, in: Early Music 20/1
(1992), pp. 64–68.
19 Church music was often scored for a ‘Kirchentrio’ of two violin parts and one
bass part, without the viola. The bass part could be performed without cellos.
20 MBA, III/290.
21 See fn. 19.
22 Edge, Mozart’s Viennese Orchestras (see fn. 18), p. 68. Edge furthermore notes
that in Vienna “the soprano and alto parts in several churches were sung by women”.
23 Edge, Mozart’s Viennese Orchestras (see fn. 18), p. 80.
24 Zaslaw, Mozart’s Symphonies (see fn. 18), p. 463–465.
25 See the Critical Report, pp. 173f.
26 Leopold Mozart, Gründliche Violinschule. Faksimile-Reprint der 3. Auflage 1789,
Wiesbaden, 1983. Clive Brown, Dots and strokes in late 18th- and 19th-century
music, in: Early Music 21/4 (1993), pp. 593–610. Robert Riggs, Mozart’s Notation of Staccato Articulation: A New Appraisal, in: The Journal of Musicology XV/2
(1997), pp. 230–277. Clive Brown, Classical and Romantic Performing Practice
1750–1900, Oxford, 1999, pp. 200–227.